This invention relates to fuel systems and more particularly to a filler pipe arrangement for an automotive fuel tank or the like.
Automotive fuel tanks are refuelled by means of a filler pipe that carries a detachable cap at the open end of the filler pipe. This detachable gas cap is customarily designed to seal the open end of the filler pipe when it is installed. However, there are instances when the gas cap is not installed properly after refuelling or forgotten altogether.
This is an undesirable situation for many reasons particularly for automotive vehicles that have an onboard diagnostic system that requires the filler pipe to be sealed in order to function properly.
My prior U.S. Pat. No. 5,322,100 issued Jun. 21, 1994 provides a fuel filler module for the filler pipe of an automotive fuel tank or the like that has a spring biased trap door that automatically seals the open end of the filler pipe when the fuel nozzle is withdrawn so that filler pipe is sealed even if the gas cap is not installed properly or forgotten after fueling.
While this filler pipe arrangement performs its intended purpose very satisfactorily, there is a further need for maintaining the pressure in the sealed fuel tank within certain limits.
U.S. Pat. No. 4,893,643 granted to William E. Gifford et al Jan. 16, 1990 recognizes that a sealed fuel tank is subject to positive pressure fluctuations due to the vaporization of liquid fuel in the fuel tank expansion of the liquid fuel and fuel vapor due to rising temperature. A positive pressure fluctuation occurs even if the fuel system includes a fuel vapor storage canister such as that disclosed in the Gifford patent. The Gifford filler pipe arrangement therefore incorporates a poppet valve to relieve high fuel tank pressures. The poppet valve, however is located next to the spring biased trap door for sealing the fuel tank thereby increasing the size of the filler pipe arrangement. Moreover, the Gifford filler pipe arrangement does not relieve undesirable negative or vacuum pressure in the sealed fuel tank that can develop due mainly to low temperature and high altitude.
On the other hand fuel caps equipped with positive and vacuum pressure relief valves are known. These fuel caps, however, are not useful in filler pipe arrangements that are sealed internally such as the filler pipe arrangements that are disclosed in my prior U.S. Pat. No. 5,322,100 and the aforementioned U.S. Pat. No. 4,893,643.